In order to achieve acceptable esthetics and provide protection from decay the margins of crowns and inlays are placed into the gum groove or sulcus. Fabrication of the crowns and inlays is accomplished on replicas of properly prepared teeth which are made from impressions rendered in a variety of materials. In order that these impressions register the end or finish lines of said crowns or inlays the gum margin must be temporarily retracted. Two methods are in common use: packing with cord and electrosurgery. The latter has many advantages but execution with existing electrodes is subject to a severe limitation which does not allow the technique to realize its potential and makes it essentially destructive and unpredictable.
The problem involves the following impasse: in order to get any tactile feedback the tooth must be used as a guide. However, any contact with the tooth incinerates the surface of the cementum, and destroys the epithelial attachment--the connection of the gum to the tooth root.